Update y axis pseudolandmarks

[HaleySchuhl]

Describe your changes
Move function into homology sub-package and remove the obj input parameter.

Type of update
Is this a:

• New feature or feature enhancement
• Work in progress

Associated issues
#945

Additional context
Add any other context about the problem here.

For the reviewer
See this page for instructions on how to review the pull request.

• PR functionality reviewed in a Jupyter Notebook
• All tests pass
• Test coverage remains 100%
• Documentation tested
• New documentation pages added to plantcv/mkdocs.yml
• Changes to function input/output signatures added to updating.md
• Code reviewed
• PR approved

[codecov]

Codecov Report

Merging #1185 (d4f266e) into release-4.0 (2efd7fd) will not change coverage.
The diff coverage is 100.00%.

@@              Coverage Diff              @@
##           release-4.0     #1185   +/-   ##
=============================================
  Coverage       100.00%   100.00%           
=============================================
  Files              174       174           
  Lines             7730      7729    -1     
=============================================
- Hits              7730      7729    -1     

Flag	Coverage Δ
unittests	100.00% <100.00%> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
plantcv/plantcv/__init__.py	100.00% <ø> (ø)
plantcv/plantcv/homology/__init__.py	100.00% <100.00%> (ø)
plantcv/plantcv/homology/y_axis_pseudolandmarks.py	100.00% <100.00%> (ø)

... and 1 file with indirect coverage changes